Fiber-reinforced plastic (FRP) attracts attention in various industrial fields as light-weighted and high-strength material. In recent years, to produce a relatively large fiber-reinforced plastic molding at a low cost, there has been employed a vacuum assist resin transfer molding (VaRTM) for molding fiber-reinforced plastic under a pressure-reduced atmosphere by means of vacuum absorption. The vacuum assist resin transfer molding is a method for obtaining a fiber-reinforced plastic molding including the steps of covering a dry fiber fabric arranged in a molding die with a bag film, vacuum-absorbing the bag film, infusing a liquid resin into the bag film, impregnating the fiber fabric with resin, and curing the resin (for example, refer to PTL1: Japanese Patent Laying-Open No. 60-83826).
However, since a dry fiber fabric has no tackiness (viscosity), the dry fiber fabric itself cannot be fixed at a position against gravity in the step of forming into a three-dimensional shape (the step of arranging a dry fiber fabric on a molding die, the step of laminating a dry fiber fabric on a dry fiber fabric, and the like). Further, when a dry fiber fabric and a molding die, or a dry fiber fabric and a dry fiber fabric are not in sufficient contact with each other, fibers in some cases exhibited wrinkles under the pressure-reduced condition.
As a simplified method for solving such a problem, a method is conceivable using a tape to fix a portion being subject to trimming and not eventually used in a finished product. However, there is a problem that a portion which can be fixed using a tape is limited, and that the operation is cumbersome and results in low productivity.
Therefore, there have been proposed a method for fixing a dry fiber fabric with use of solution with a binder containing an amorphous thermoplastic resin (tackifier: spray) (for example, refer to PTL2: Japanese Patent Laying-Open No. 2004-269705) and a method for shortening the step of laminating dry fiber fabrics by adhering a plurality of fiber fabrics each other in advance by means of an adhesive resin composed of a mixture of a thermoplastic resin (toughness) and thermosetting resin (for example, refer to PTL3: Japanese Patent Laying-Open No. 2004-114586).
The method disclosed in PTL2 can be used in the step of arranging a dry fiber fabric on a molding die and in the step of laminating a dry fiber fabric on a dry fiber fabric, allowing the operation time to be shortened. However, when the method is used in the step of arranging a dry fiber fabric on a molding die, a non-cured thermoplastic component is exposed at the surface of a demolded fiber-reinforced plastic molding. Therefore, there has been a problem that the surface which was in contact with the molding die may become sticky and that a thermoplastic component may exhibit white dots to cause poor appearance.
Further, the method disclosed in PTL 3 can be used in the step of laminating a dry fiber fabric on a dry fiber fabric, allowing the operation time to be shoretened. However, the method cannot be used in the step of arranging a dry fiber fabric on a molding die. Further, when a plurality of fiber fabrics are combined in advance, and a large number of layers are present, shaping with respect to a bent portion becomes difficult. Particularly, the tension applied to the fiber will differ between the inside and outside, resulting in occurrence of wrinkles due to loosening of fibers.